Microstructure of retrievals made from standard cast HC-CoCrMo alloys

Priska Stemmer, Robin Pourzal, Yifeng Liao, Lawrence Marks, Michael Morlock, Josh J. Jacobs, Markus A.wimmer, Alfons Fischer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

14 Scopus citations

Abstract

During the past decade, self-mating metal bearings based on cobalt- chromium-molybdenum (CoCrMo) alloys have become very popular in total hip replacements and hip resurfacings. This led to a market share of more than 35 % for metal-on-metal (MoM) bearings in the United States before several cases of high wear with biologic consequences led to a sharp drop in popularity. In part, these failures are a result of a very shallow understanding of the wear mechanisms in MoM joints and their relation to the microstructure. In order to find such a relation, one has to keep in mind that the microstructures of metallic materials depend distinctly on the entire production sequence. In addition, they change markedly under tribological stresses. This paper does not discuss the wear of any specific retrieval or even try to relate that to the specific microstructure, because such a task would be impossible based on the unknown loading history of such retrievals. Thus, we depict only the possible range of microstructures from standardized high carbon (HC)-CoCrMo retrievals. These reveal different types of hard phases: carbides and/or intermetallic phases. Some are fine (<10μm) and homogeneously distributed, whereas others appear as thin (<1 μm) and brittle cord-shaped arrangements at grain or dendrite boundaries. Coarser (>30 μm) types of mixed hard phases, which consist of carbides and interme-tallic phases, often show microcracks already below the articulating surfaces. Such subsurface microcracks are known to destabilize the gradient below the surface and the balance between tribochemical reactions and surface fatigue. In this paper, the microstructures of retrievals manufactured from standard cast CoCrMo alloys are shown and evaluated.

Original languageEnglish (US)
Title of host publicationMetal-on-Metal Total Hip Replacement Devices
PublisherASTM International
Pages251-267
Number of pages17
ISBN (Print)9780803175464
DOIs
StatePublished - 2013
EventASTM Symposium on Metal-on-Metal Total Hip Replacement Devices - Phoenix, AZ, United States
Duration: May 8 2012May 8 2012

Publication series

NameASTM Special Technical Publication
Volume1560 STP
ISSN (Print)0066-0558

Other

OtherASTM Symposium on Metal-on-Metal Total Hip Replacement Devices
CountryUnited States
CityPhoenix, AZ
Period5/8/125/8/12

Keywords

  • Carbides
  • Cast
  • Cocrmo
  • Intermetallic phases
  • Metal-on-metal
  • Microstructure
  • Mom
  • Wear

ASJC Scopus subject areas

  • Materials Science(all)

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